They chose a narrow, open ended channel which is as little as 20ft wide in places on an “inland sea” between RAF Valley and Holyhead. The spot is a kayakers’ favourite.

“It’s like a very fast flowing river. A large volume of white, fluffy and aerated water is channelled along it.”

The volunteers practised rescuing a casualty in a “man overboard” drill.

They also used their bodyweight in lifeboats to practise turns in tight spaces in fast flowing water. The ten volunteers used a standard D-class inshore lifeboat and an Arancia rigid inflatable boat.

Robin Goodlad, RNLI flood response manager who helped rescue two people in Aberystwyth floods in June, said that the exercises have been beneficial.

“The volunteers had been a little bit anxious but this has built their confidence. They’ve been training on how they get people out of the water.

“They have also been trained on extracting a casualty from a dangerous situation such as near a weir. The volunteers will lash two boats together well away from the weir and a rope will be thrown to the casualty.”